1. Field of the Invention
The present invention relates to computing systems. More specifically, the present invention relates to systems and techniques for updating computing systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Computing systems typically include a microprocessor which controls input and output operations of numerous associated peripheral devices in accordance with a scheme (or BIOS, "basic input and output system") stored as microcode in a memory associated therewith. As the need to change the input/output control scheme changes, it is desirable to change the microcode by which these functions are performed by the microprocessor. This is typically accomplished by changing the microcode which controls the processor. However, this has been somewhat problematic.
For example, storage controllers (or "storage control units"), such as the 3990 unit sold by the International Business Machines (IBM) Corporation, typically include two clusters which allow access to a single set of direct access storage devices (DASDs). Each of the clusters are on a separate power boundary and each has the ability to load its own microcode. Each cluster has two microprocessors and each microprocessor provides a separate path to the storage devices. Within each microprocessor, microcode regulates access by the host to the storage device.
The traditional method of updating the microcode in each cluster involves a disruption in the operation of the cluster while the microcode is loaded and the cluster is reinitialized. The procedure may take up to one-half hour per cluster in the conventional system. In this context, "disruptive" implies that the customer losses access to the data behind the control unit until the new microcode has been loaded into both clusters using a power on/reset. Hence, lengthy service disruptions are generally undesirable.
An alternative, though no less undesirable, approach is to limit the updating microcode to small changes. However, this is not practical where significant and substantial changes in the microcode are in order.
Thus, there is a need in the art for a technique for substantially updating microcode with minimal disruption in the operation of a control processor.